The use of zinc ions to control the size of Yb/Er:KMnF3 nanocrystals with single band emission

Abstract

Yb/Er co-doped KMnF₃ nanocrystals (NCs) exhibit strong single band emission centered at 660 nm, which is beneficial for bio-imaging application. It is known that the bio-distribution, clearance rate, and elimination pathway of intravenously injected NCs are strongly associated with the particle size. Here, we provide a novel method to modify the size of Yb/Er:KMnF₃ NCs by introducing Zn²⁺ in the initial solution. Through changing the concentration of Zn²⁺ (0–30 mol%), the size of Yb/Er:KMnF₃ NCs with cubic phase KMnF₃ can be easily tuned from 8 nm to 18 nm. Interestingly, the Zn²⁺ ions were not incorporated into the lattice structure or adhered on the surface of the final NCs; they just helped the growth of Yb/Er:KMnF₃ NCs. Combined with the upconversion emission spectra results, we can provide a direct evidence for the size-dependent upconversion luminescence on account of the final NCs with different sizes having the same components, shape, crystal structure and crystallinity.